A high-performance calculator called a super-computer generates a large amount of heat at it operates. When the temperature of the calculator exceeds a permissible upper-limit temperature, a failure, such as, for example, a malfunction, a trouble, or a reduction in processing capability occurs. Therefore, means for cooling the calculator is required.
In general, a water-cooling type cooling apparatus is adopted to cool a high-performance calculator. In the water-cooling type cooling apparatus, the cooling apparatus and the calculator are connected to each other via a pipe such that heat generated from the calculator is transported to the cooling apparatus by cooling water (refrigerant) to be radiated from the cooling apparatus to the atmosphere.
Since a lot of power is used to cool the high-performance calculator, a reduction in power consumed by the cooling apparatus is requested from the view point of energy saving. In order to reduce the power consumption of the cooling apparatus, it may be considered that the cooling capability of the cooling apparatus is changed depending on the operating state of the calculator, for example.
However, although the amount of heat generated in the calculator is suddenly changed depending on the operating state of the calculator, it is difficult to suddenly change the cooling capability of the cooling apparatus.
Thus, there has been proposed a technology in which a bypass pipe and a flow regulating valve are provided between a pipe of a cooling water outlet side and a pipe of a cooling water inlet side of the cooling apparatus so that an opening degree of the flow regulating valve is regulated depending on the temperature of the cooling water supplied to the calculator. Herein, water or other refrigerants used for cooling the calculator are referred to as the “cooling water,” for convenience.
However, the power of the cooling apparatus is not sufficiently saved simply by regulating the opening degree of the flow regulating valve depending on the temperature of the cooling water supplied to the calculator.
The followings are reference documents.    [Document 1] Japanese Laid-Open Patent Publication No. 60-138382, and    [Document 2] International Publication Pamphlet No. WO 2004/079805.